Search Results (10)

Herein, a three-dimensional mathematical model was established to investigate the metallurgical behavior of liquid steel in a funnel-shaped mold equipped with single-ruler electromagnetic braking (EMBr). The effects of mold thicknesses, electromagnetic intensity, and casting speed in flow behavior were investigated. The results indicate that with EMBr, multiple pairs of induced current loops are present in the horizontal section of the magnetic pole center, distributed in pairs between the jets and broad faces. The Lorentz force acting on the main jet, which impacts the downward and upward flow at adjacent broad faces, is opposite in direction. Increasing mold thickness results in a larger jet penetration depth, leading to a higher meniscus temperature near the narrow faces accompanied by elevated velocity and turbulent kinetic energy. EMBr can lead to a decrease in shell thickness and an improvement in its uniformity at mold exit. For the thickened mold, as the magnetic flux density increases and the casting speed decreases, the penetration depth of jets and velocity near the narrow faces and meniscus decreases. The shell thickness decreases as the casting speed increases, with the lowest non-uniformity coefficient of 6.78% observed at a casting speed of 5.0 m/min. Full article

As the third generation of thin slab continuous casting and rolling technology, endless strip production (ESP) has been widely used in the steelmaking industry. The key equipment in this process, the funnel-type mold, is prone to accidents such as slag entrainment, surface cracks and steel leakage under high casting speed conditions. To reduce the incidence of the above accidents, the numerical model of flow, heat transfer and solidification in the funnel-type mold is established by using the k-ε model, enthalpy–porosity method and magnetohydrodynamics (MHD), and the influence mechanism of the mold cavity and submerged entry nozzle (SEN) on the molten steel is studied, providing a new solution for optimizing the ESP process. The results show that compared with the type-I mold, the influence of the geometric disturbance of the top cavity on the flow state of the middle and lower body is localized, while the type-II funnel mold increases the thickness of the solidified shell at the outlet of mold; the marked enhancement in solidified shell thickness and uniformity at the mold exit achieved through the type-II SEN due to the distribution of temperature and velocity are more reasonable, reducing the risk of surface cracks and steel leakage. Full article

Understanding the phenomena that cause jet oscillations inside funnel-type thin-slab molds is essential for ensuring continuous liquid steel delivery, improving flow pattern control, and increasing plant productivity and the quality of the final product. This research aims to study the effect of the nozzle’s internal design on the fluid dynamics of the nozzle-mold system, focusing on suppressing vorticity generation below the nozzle’s tip. The optimized design of the nozzle forms the basis of the results obtained through numerical simulation. Mathematical modeling involves fundamental equations, the Reynolds Stress Model for turbulence, and the Multiphase Volume of Fluid model. The governing equations are discretized and solved using the implicit iterative-segregated method implemented in FLUENT^®. The main results demonstrate the possibility of controlling jet oscillations even at high casting speeds and deep dives. The proposed modification in the internal geometry of the nozzle is considered capable of modifying the flow pattern inside the mold. The geometric changes correspond with 106% more elongation than the original nozzle; the change is considered 17% of an inverted trapezoidal shape. Furthermore, there was a 2.5 mm increase in the lower part of both ports to compensate for the inverted trapezoidal shape. The newly designed SEN successfully eliminated the issue of jet oscillations inside the mold by effectively preventing the intertwining of the flow. This improvement is a significant upgrade over the original design. At the microscale, a delicate force balance occurs at the tip of the nozzle’s internal bifurcation, which is influenced by fluctuating speeds and ferrostatic pressure. Disrupting this force balance leads to increased oscillations, causing variations in the mass flow rate from one port to another. Consequently, the proposed nozzle optimization design effectively controls microscale fluctuations above this zone in conjunction with changes in flow speed, jet oscillation, and metal–slag interface instability. Full article

When the casting speed of the thin slab continuous caster is increased, the ratios of the solid and liquid phases in the solidification front of the molten steel in the mold change, which affects the thickness of the solidified shell. In order to accurately calculate the thickness of the solidified shell and determine the value range of the mushy zone coefficient suitable for the mathematical model of solidification heat transfer at high casting speed, this paper established the solidification heat transfer mathematical model in thin slab funnel mold, and the influence of different mushy zone coefficients on the accuracy of solidification heat transfer mathematical model was analyzed and compared with the actual solidified shell thickness. The results showed that, when the casting speed was increased to 4~6 m/min and the coefficient of the mush zone coefficient was 3 × 10⁸~9 × 10⁸ kg/(m³⋅s), the thickness of solidified shell calculated by the solidification heat transfer model was in good agreement with that measured in practice. The research in this paper provides an important reference for the establishment of the solidification heat transfer mathematical model at high casting speed in the future. Full article

In thin-slab continuous casting, due to the influence of the special shape of the funnel mold, cracks at the corner of the slab shell are more likely to occur than those in conventional slab shells, and a serious wear phenomenon also appears on the narrow face of the copper wall of the mold. Aimed at the corner cracks of thin slabs and the wear phenomenon of the copper wall, a new 3D stress analysis model in a funnel mold has been developed to simulate the stress-–train behavior of the slab shell under high-speed continuous casting. The results show that at the position 600 mm below the meniscus, the gap begins to appear at the corner of the slab; the maximum value of the first principal stress appears at the corner. The shell is squeezed by the copper wall during the downward movement in the funnel mold, and the slab shell in the funnel area moves towards the narrow face. The displacement causes the deformation of the slab shell to extend to the corners, the deformed shell is pressed against the corner of the copper wall. A new type of copper wall was designed for production, and it was found that the cracks at the corner of the slab shell were greatly reduced. Full article

In this study, a funnel mold (FM) model of a multi-mode electromagnetic braking (EMBr) device was developed, and the magnetic flux density at different currents was obtained by MAXWELL software. By using the magnetohydrodynamics (MHD) module of FLUENT software, the volume of fluid binomial flow turbulence model and the EMBr mathematical model of the steel/slag flow field were coupled, and the characteristics of the molten steel flow and the liquid-level fluctuation in the 1520 mm × 90 mm FM with the casting speed of 6 m/min were calculated under the effect of the electromagnetic field. The FM liquid-level characteristic information under production conditions was obtained in a nail board industrial experiment and compared with the magnetic-fluid coupling model. The results show that the EMBr can significantly change the flow behavior of molten steel. When the magnetic pole current is not less than 800-600 A, the maximum liquid-level fluctuation height decreases from 18 mm without EMBr to less than 5 mm, and the liquid-level cannot easily entrap slag. Considering the EMBr effect and production cost, the reasonable magnetic pole current should be 800-600 A. The reliability of numerical simulation was also verified by the industrial test results of the nail board. Full article

For the purpose of studying compact strip production (CSP) funnel-shaped mold and flexible thin-slab rolling (FTSR) funnel-shaped mold, a three-dimensional (3D) multi-field coupling mathematical model was established to describe the electromagnetic braking (EMBr) continuous casting process. To investigate the metallurgical effect of EMBr in the CSP and FTSR funnel-shaped thin-slab molds, a Reynolds-averaged Navier–Stokes (RANS) turbulence model, together with an enthalpy–porosity approach, was established to numerically simulate the effect of ruler EMBr on the behaviors of melt flow, heat transfer, solidification, and inclusion movement in high-speed casting. The simulation results indicate that the application of ruler EMBr in the CSP and FTSR molds shows great potential to improve the surface temperature of molten steel and reduce the penetration depth of downward backflow. This contributes to the melting of the slag rim near the meniscus region and facilitates the floating removal of the inclusions in the molten pool. In addition, in comparison with the case of no EMBr, the parametric study shows that the braking effect of ruler EMBr with an electromagnetic parameter of 0.5 T can enhance the upward backflow in the two high-speed thin-slab molds. The enhanced upward backflow can successfully entrain the inclusions to the top of the mold and improve the activity of surface fluctuations to avoid the formation of the slag rim. For instance, for the ruler EMBr applied to the FTSR mold, the maximum amplitude of surface fluctuation and the floatation removal quantity of inclusions with a diameter of 100 μm are increased by 4.6 percent and 51 percent, respectively. Full article

Self-compacting concrete (SCC) has been developed as a type of concrete capable of filling narrow gaps in highly reinforced areas of a mold without internal or external vibration. Bleeding and segregation in SCC can be prevented by the addition of superplasticizers. Due to these favorable properties, SCC has been adopted worldwide. The workability of SCC is closely related to its yield stress and plastic viscosity levels. Therefore, the accurate prediction of yield stress and plastic viscosity of SCC has certain advantages. Predictions of the shear stress and plastic viscosity of SCC is presented in the current study using four different ensemble machine learning techniques: Light Gradient Boosting Machine (LightGBM), Extreme Gradient Boosting (XGBoost), random forest, and Categorical Gradient Boosting (CatBoost). A new database containing the results of slump flow, V-funnel, and L-Box tests with the corresponding shear stress and plastic viscosity values was curated from the literature to develop these ensemble learning models. The performances of these algorithms were compared using state-of-the-art statistical measures of accuracy. Afterward, the output of these ensemble learning algorithms was interpreted with the help of SHapley Additive exPlanations (SHAP) analysis and individual conditional expectation (ICE) plots. Each input variable’s effect on the predictions of the model and their interdependencies have been illustrated. Highly accurate predictions could be achieved with a coefficient of determination greater than 0.96 for both shear stress and plastic viscosity. Full article

The turbulent phenomena occurring in the thin slab mold affect the final product quality. Therefore, it is essential to carry out studies to understand and control their occurrence. Current research aims to study the electromagnetic brake (EMBr) effects on the flow patterns in a funnel thin slab mold. The objective is to prevent the detrimental phenomenon known as dynamic distortions (DD) of the flow, applying the EMBr in the typical horizontal position (H-EMBr) and a new vertical position close to the narrow faces (V-EMBr). The fluid dynamics are simulated using the Reynolds stress model (RSM), the Volume of Fluid (VOF) model and the Maxwell equations in their magnetohydrodynamics (MHD) simplification. The results show that the H-EMBr effectively counteracts the DD phenomenon by reducing the submerged entry nozzle (SEN) ports' mass flow rate differences. The EMBr reduces the highest meniscus fluctuations from −10 to ±3 mm with a field intensity of 0.1T and almost 0 mm for higher field intensities. In contrast, the V-EMBr configuration does not reduce or control at all the DD phenomenon, even though eliminating the upper roll flows does not diminish the meniscus fluctuation amplitudes and induces new small roll flows close to the SEN's wall. Full article

The flow transport of a 420 × 320 × 90 mm beam blank continuous casting mold that used open-stream pouring combined with submerged refractory funnels was studied. By considering the dynamic similarity, geometric similarity, and air entrapment quantity similarity, a full-size water model was established. Meanwhile, the 3D mathematical models that included three phases were applied. Through the combination of the water model and the mathematical model, the distribution and morphology of the phases in the mold were investigated. The results indicate that bubbles existed in the molten steel due to entrapment and the flow pattern was different from that of the full protection-poured mold. Furthermore, the effects of funnel immersion depth and funnel diameter on the bubbles’ impact depth, funnel’s inside wall shear stress, and overall area of the air/steel interface were discussed. The results provide useful information for the industrial continuous casting process. Full article